Spark plug



June 11, 1935. w. E. 'LETTERMAN SPARK PLUG Filed July 6, 1932 v I venlorfl izA-am zlezz'rmn .accumulations and carbon,

Patented June 11, 1935 UNITED STATES PATENT OFFICE 9 Claims.

My invention relates to improvements in spark plugs, and particularly to a spark plug having a valved conduit for admitting. air therethrough into the interior of the combustion chamber of an internal combustion engine upon which it may be mounted.

It is an important object of my invention to provide a spark plug of t e type described having air passing means controlled by check valve means operable to admit air upon the intake stroke of the piston of the engine whereby a stream of air is impinged upon the starting points of the plug so as to clean themand prevent the formation of carbon thereon and the fouling thereof.

It is also an important object of my invention to provide a spark plug as described above whereby air is introduced into the combustion chamber so as to scavange the combustion chamber of oil and by this means in conjunction with the cleaning of the sparking points, to increase the efiiciency and economy of operation .of the engine.

It is also an important object of my invention to provide a spark plug construction as described above whereby the sparking point thereof are kept clean and cool by the impinged stream of air thereby prolonging the useful life of the spark plug and its greatest efliciency, resulting in continual perfect combustion in the engine.

Other objects and advantages of my invention will be apparent from a reading of the following description in connection with the drawing,

wherein for purposes of illustration I have shown a preferred embodiment of the invention.

In the drawing: Figure 1 is a transverse vertical sectional view through an embodiment of the invention.

Figure 2 is a transverse horizontal sectional view therethrough.

Referring in detail to the drawing, wherein like numerals refer to like parts throughout the same, the numeral 5 generally designates the body portion of the spark plug construction. This comprises the usual wrench grip 5 below which is the cylinder head engaging annulus 1 from which depends the reduced exteriorly screw-threaded skirt 8 for projecting into the combustion chamber. On one side of the lower edgev of the skirt 8 is the usual electrode 9 projecting toward the center of the opening in the skirt. A conven- .tional type of composition insulator I is en gaged with the body portion of the spark plug in the usual manner, and is retained and assembled by means of the annular nut ll engaged the construction of the insulator Hi and its elec-.

trode, and the manner in which the electrode is associated with the other electrode 9.

The insulator I0 is provided axially throughout its length with an opening I! in which is disposed a tubular electrode l3. In the upper part of the insulator I0 is an enlarged bore H in which is seated a tubular cage l which is open at its upper end and provided in its bottom with a threaded opening into which a portion on the upper end of the electrode I3 is threaded as indicated at l6. This communicates the upper end of the electrode l3 with the interior of the cage 15. A ferrule 11 having a portion located and secured in a countersink in the upper end of the insulator l0 surrounds the upper portion of the cage IS with which itis engaged. The ferrule I! has its upper part exteriorly screw-threaded as indicated at l8 whereby to receive a cap l9 threaded thereon for confining a suitable washer or cushion 20 which is seated in the ferrule and upon the upper edge of the cage IT. The cap I9 has upwardly projecting therefrom a threaded boss 2| which constitutes the mounting-for the binding post nut 22 seated therein by the action of a helical spring 25 acting between the bottom of the cage 15 and the ball as shown. The tension of the spring 25 need only be suflicient to maintain the ball seated under normal conditions.

When the plug is installed on an engine, the down stroke or intake stroke of the piston will create a suction in the tubular electrode such as will unseat the check ball 24 and draw through the top of the plug a volume of air into the combustion chamber. It will be obvious, since the terminal of the electrode 9 is placed at the opening of the lower end of the tubular electrode l3, that the incoming air will impinge upon the terminal of the electrode 9 ard also create a cleaning agitation about the lower end of the elecof the electrode l3 projects slightly below the lower extremity of the insulator l0.

It will be observed that the arrangement is such that when the stream of air is produced in the manner described, that air will be introduced into the combustion chamber and in its passage thereinto will clean and cool the electrodes of the spark plugs, whereby to produce the effects sought herein.

Though I have shown and described herein a preferred embodiment of the invention, it is to be definitely understood that I do not desire to limit the application of the invention thereto, and any change or changes may be made in material and structure and arrangement of parts, within the spirit of the invention and the scope of the subjoined claims.

What is claimed is:-

- 1. In a ventilated spark plug an insulated core having a relatively small bore, said bore having its outward end portion considerably increased in diameter and defining a chamber having a shoulder, an electrode in said bore, said electrode comprising a conductive tube received in said bore and having the inner end portion extending beyond the inner end of said core, said electrode further comprising a conductive cage located within said chamber and having its inner end seated on said shoulder, said inner end of the cage having an opening in which the outer end of said tube is inserted and secured, an annular valve seat abutting the open outer end of said cage and seated in the outer end of said chamber, a cap connected with the .outer end portion of said core and abutting said valve seat and the outer end of said core thereby holding said cage and valve seat in place, a ball check yieldably engaged and seated with said valve seat, and a helical spring having one end engaged with the inner end of said cage and the opposite end engaged with said ball check.

2. In a ventilated spark plug, an insulated core provided with a bore, said bore having a considerably enlarged outer end portion, an electrode comprising a conductive tube located in said bore and having an outer portion extending into said enlarged portion of the bore, a valve cage in said enlarged portion and having a threaded opening in its inner end receiving and ing the outer end of said core and with said cushion for holding said cushion in place.

3. In a ventilated spark plug, an insulated core provided with a bore, said bore having a considerably enlarged outer end portion, an electrode comprising a conductive tube located in said bore and having an outer portion extending into said enlarged portion of the bore, a valve cage in said enlarged portion and having a threaded opening in its inner end receiving and connecting said outer portion of the tube, the remaining end of said cage being open, a valve cushion abutting said remaining end of the cage and having an air passage therethrough communicating with a valve seat thereon, a ball cooperable with said seat for opening'and closing said passage, a heli cal spring within said cage and expanding between the inner end of said cage and said ball to hold the ball yieldably engaged with said seat, and tubular means engaging the outer end of said core and with said cushion for holding said cushion in place, said tubular means comprising a ferrule having a portion anchored in a portion of said enlarged portion of said bore and engaging and surrounding said cage and said cushion, and acap threaded on another portion of said ferrule and engaging said cushion, said cap having an air passage therethrough which communicates with the air passage in said cushion.

4. In a ventilated spark plug an insulated core provided with a bore, said bore having a considerably enlarged outer end portion, an electrode comprising a conductive tube located in said bore and having an outer portion extending into said enlargedportion of the bore,'-a' valve cage in said enlargedportion and having a.v

threaded opening in its inner end receiving and connecting said outer portion of the tube, the remaining end of said cage being open, a valve cushion abutting said remaining end of the cage and having an air passage therethrough communicating with a valve seat thereon, a bell cooperable with said seat for opening and closing said passage, a helical spring within said cage and expanding between the inner end of said cage and said ball to hold the ball yieldably engaged with said seat, and tubular means engaging the outer end of said core and with said cushion for holding said cushion in place, said tubular means comprising a ferrule having a portion anchored in a portion of said enlarged portion of said bore and engaging and surrounding said cage and said cushion, and a cap threaded on another portion of said ferrule and engaging said cushion, said cap having an air passage therethrough which communicates with the air passage in said cushion, said cap including a threaded neck traversed by said air passage and arranged to receive thereon a binding post nut.

5. A spark plug comprising an insulator provided with an axial bore, a tubular electrode extending in the bore, said tubular electrodehaving its upper part formed to provide a valve cage containing spring pressed valve means, a ferrule around said valve cage and connected with the insulator, a removable valve seat resting on and closing the upper end of said valve cage and confined by said fen'ule, a cap threaded on said ferrule and engaging the upper side of said valve seat, said valve seat being provided with an opening therethrough normally closed by said spring pressed valve means, said opening being in communication with a passage provided in said cap, said passage communicating with the atmosphere. 1 6. In a. spark plug including an insulator provided with a bore, a tubular electrode in said bore, the upper end of said tubular electrode having a valve cage containing spring pressed valve means; a removable valve seat abutting and closing the upper end of the valve cage, a ferrule around and engaging the valve cage and connected with the insulator, said ferrule confining the valve seat in place, said valve seat being provided with an opening normally engaged and closed by said spring pressed valve means, and an open tubular cap threaded on said ferrule and abutting the upper side of the valve seat and hold- ,ing the valve seat on the upper end of the cage.

7.. A spark plug comprising an insulator provided with an axial bore, a tubular electrode extending in said bore, a valve cage connected to the upper end of said electrode and in communication therewith, a removable valve seat eng ing and closing the upper end of said cage, said cage containing spring pressed valve means normally engaging and closing an opening provided through said valve seat, a ferrule connected to said insulator around said cage and confining said valve seat, and a tubular cap threaded on said ferrule and engaging the upper side of said valve seat.

8. A spark plug comprising an insulator provided with an axial bore, a tubular electrode extending through said bore, the upper end of the electrode being formed to provide a valve cage open at its upper end, a ferrule on the upper end of the insulator around the cage, a removable valve seat confined by said ferrule and resting on the upper end of said cage and closing the same, said valve seat being provided with an opening communicating with the interior of said cage, and

' electrode a cap threaded on said ferrule and having a part abutting the upper side of said valve seat and holding the valve seat in place.

9. A spark plug comprising an insulator provided with an axial bore, a tubular electrode extending through said bore, the upper end of the being formed to provide a valve cage open at its upper end, a ferrule on the upper end of the insulator around the cage, a removable valve seat confined by said ferrule and resting on the upper end of said cage and closing the same, said valve seat being provided with an opening communicating with the interior of said cage, and a cap threaded on said ferrule and having a part abutting the upper side of said valve seat and holding the valve seat in place, said cap including a tubular stem communicating at its lower end with said opening in the valve seat and its upper end with the atmosphere.

WILLIAM E. LE'I'I'EmMAN. 

